[NASA] It was the famed astronomer Galileo whose study of gravity spawned the legendary tale of the Leaning Tower of Pisa "feather drop." (The story is legendary in that historians believe the account may not be true.) However, as the story goes, Galileo held a feather and a stone in either hand and released them simultaneously. Because the feather's structure slowed its descent in parachute fashion, the stone reached Earth first. Had both been released above the Moon's surface, where no air exists, each would have struck lunar firmament simultaneously. It was not until Astronauts David Scott and Jim Irwin conducted Galileo's experiment on the Moon during their Apollo 15 mission that the experiment could be duplicated in the lunar environment [NASA].
No-one had to go to the Moon to prove Galileo correct. All NASA had to do was used their massive vacuum chamber to conduct the same experiment. And, of course, they did.
So easy to setup that experiment in this huge vacuum chamber built by NASA in 1966. Three years before Apollo 11.
Brian Cox: Feather experiement in the chamber above.
I have conducted this experiment with all manner of objects in a room with a calm atmosphere. Each set of two different massed objects hit the floor from 2 meters at the same time. No need for a vacuum.